Congenital cytomegalovirus (cCMV) is the most common infectious cause of congenital malformations in Denmark. The disease is not notifiable, and there are no national data. A regional Danish prospective study from the 1970s found a cCMV incidence of 0.4%. We propose three algorithms for microbiological diagnosing: 1) Testing of pregnant women should only be -applied, when symptoms compatible with CMV infection are present, and no other diagnoses are found. 2) In children less than three weeks of age urine is the -preferred sample. 3) Retrospectively, cCMV may be diagnosed on dried blood spots, if the mother is CMV IgG-positive.